#d1 {
    width: 100px;
    height: 100px;
    margin-top: 20px;
    margin-bottom: 20px;
    background-color: red;
}

#d2 {
    width: 100px;
    height: 100px;
    margin-top: 10px;
    background-color: blue;
}

#outer {
    width: 200px;
    height: 200px;
    background-color: red;
    margin-top: 20px;
}

#inner {
    width: 50px;
    height: 50px;
    background-color: blue;
    margin-top: 10px;
}